Abstract
Skin injury response to near-infrared (NIR) laser radiation between the minimum visible lesion threshold and ablation onset is not well understood. This study utilizes a 1070-nm diode-pumped Yb-fiber laser to explore the response of excised porcine skin to high-energy exposures in the suprathreshold injury region without inducing ablation. Concurrent high-speed videography is employed to determine a dichotomous response for three progressive damage categories: observable surface distortion, surface bubble formation due to contained intracutaneous water vaporization, and surface bubble rupture during exposure. Median effective dose (ED50) values are calculated in these categories for 3- and 100-ms pulses with beam diameters (1 / e2) of 3mm (28, 35, and 49 J / cm2) and 7mm (96, 141, and 212 J / cm2), respectively. Double-pulse cases are secondarily investigated. Experimental data are compared with the maximum permissible exposure limits and ablation onset simulated by a one-dimensional multiphysics model. Logistic regression analysis predicted injury events with ∼90 % of accuracy. The distinction of skin response into progressive damage categories expands the current understanding of high-energy laser safety while underlining the unique biophysical effects during induced water phase change in tissue. These results prove to be useful in the diagnosis and treatment of NIR laser injuries.
Highlights
Advances in diode-pumped, solid-state, and fiber lasers have brought high-energy applications in the near-infrared (NIR) band to the forefront
The technique is limited in that only one independent variable can be used. This variable typically assumes the form of radiant exposure (J∕cm2), which takes into account the exposure time, duty cycle, pulse duration, power, and beam diameter
Progressive injury categories were utilized for determining suprathreshold tissue damage, as opposed to the traditional minimally visible lesion assessment
Summary
Advances in diode-pumped, solid-state, and fiber lasers have brought high-energy applications in the near-infrared (NIR) band to the forefront. The potentially hazardous nature of laser exposure is well established, with regard to possible injurious biological effects to the skin. Due to increased deployment of high-powered NIR lasers in medical, industrial, and military applications, there exists significant motivation for accurate characterization and prediction of the suprathreshold response in skin and subcutaneous tissues. Verdaasdonk et al.[7] described a three-phase process of tissue ablation using Nd: YAG (1064 nm) and argon (488∕514.5 nm) lasers, consisting of tissue denaturation, explosive vaporization (“popcorn” effect) in conjunction with an increase in light absorption, and carbonization expanding in a cyclic fashion. LeCarpentier et al.[8,9]
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